The present invention relates to an anesthetic and a method for making the anesthetic. More specifically, the present invention relates to an anesthetic containing propofol as its active component for use in veterinary applications.
Anesthetics are useful in surgical procedures to artificially produce unconsciousness or to reduce sensitivity to pain. Anesthetics are typically viewed as primarily applicable to humans. However, anesthetics also may be administered to all types of animals to reduce pain when setting broken bones, performing internal surgery, or otherwise handling the animal.
One common method of veterinary anesthetization is to premedicate the animal with an alpha-2 agonist, such as xylazine or detomidine, and then induce anesthesia with ketamine. The ketamine anesthetic may be followed by the administration of a gas anesthetic to maintain anesthesia for the remainder of the procedure. Another common method of veterinary anesthetization is administering a thiobarbiturate mixed with glycerol guaicolate. An anesthesia gas may then be administered to maintain anesthesia for a prolonged surgical procedure.
The primary disadvantage associated with these two methods is that they require access to a gas anesthetic machine. Many surgical procedures take place in remote areas where such a machine is not available. If the inducing agent used to anesthetize is administered throughout the procedure without supplemental gas, recovery is often difficult and could be violent.
Propofol has been used in anesthetic formulations administered to humans and dogs. These propofol formulations contain a phospholipid, such as egg lecithin, which functions as an emulsifying agent. However, phospholipids are good substrates for bacterial growth. Phospholipids are also incompatible with numerous preservatives that are at least somewhat water soluble, such as benzyl alcohol. The addition of such a preservative to a formulation containing phospholipids could destroy the formulation. Without a preservative in the formulation, any excess formulation must be thrown away within a few hours of its first use. Some formulations containing phospholipids also include a chelating or sequestering agent, such as ethylenediaminetetraacetic acid (EDTA). However, EDTA is not truly an antimicrobial substance and, thus, is not as effective as a preservative in preventing microbial growth. Another disadvantage with propofol formulations currently available is that they typically contain relatively small amounts of propofol, generally less than five percent by weight/volume (w/v). Therefore, large quantities of the formulation must be administered to provide the desired anesthetic effect.
To overcome the deficiencies found with conventional anesthetics, an anesthetic formulation containing a preservative and a method for making this anesthetic formulation are needed in the art. In addition, a single anesthetic formulation that can be used to both initially anesthetize an animal and to maintain anesthetization is needed.